HANDBOOK OF CARDIAC PACING – PART 7 pdf

This includes the model, serial number and dates of implant for the pacemaker and leads.. 102 EVALUATION OF PACEMAKER MALFUNCTION The first step in evaluating pacemaker malfunction is to

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Table 10.3 Common postoperative orders

1 PA and Lateral chest X-ray within 2 hrs for lead placement and to evaluate for pneumothorax

2 Ice pack to incision site

3 IV antibiotics (usually one additional dose)

4 Oral and parenteral analgesics

5 Maintain head of bead > 30° angle

6 Resumption of diet

7 Vital signs frequently at first then tapering to routine

8 Wound dressing check for drainage and hematoma

9 Respiratory status evaluation (for pneumothorax)

10 Monitor ECG rhythm for arrhythmias, capture and appropriate sensing

11 Restrict movement of ipsilateral arm for 24 hours

12 Full pacemaker evaluation prior to discharge with activation of any special features and adjustment of the sensor if present

Table 10.4 Predischarge teaching

Wound care instructions include the following:

1 Continually assess wound for signs and symptoms of infection

2 Keep wound clean and dry for 1 week

3 Cover the incision with plastic when bathing

4 Remove steri-strips after 7 days Do not wait until they fall off

Activity restrictions:

1 No lifting greater than 10 pounds for 2 weeks

2 No repetitive arm extension over the head for 2 weeks

3 If the patient is pacemaker dependent, driving should be restricted for 2 weeks

or as determined by the physician Otherwise, 48 hours is usually sufficient to allow the patient to recover from any anesthesia and for the incisional pain to subside

Restrictions against electromagnetic interference:

1 Arc welding

2 MRI

3 Diathermy

4 Therapeutic radiation over the pacemaker

5 Electronic article surveillance scanners

6 Metal detectors

7 Supermarket checkout scanners

8 Cell phones

9 Electric blankets

Contact the pacemaker clinic if:

1 Symptoms prior to implant return

2 The pulse rate seems too slow or too fast

3 Dizziness, lightheadedness, or syncope occurs

4 Unusual shortness of breath or chest pain develops

5 Muscle twitching around the pacemaker is present

Virtually all household electrical items and power tools are safe for patients to use Sources of high electrical energy, such as arc welders, power generators, large electromagnets and the high voltage ignition system of a gasoline engine, may create enough EMI to affect pacemaker function MRI scanners are a problem for pacemakers due to the high energy radiofrequency energy fields that they gener-ate They are not likely to suck the pacemaker and wires through the chest as there

is very little ferrous metal in these devices other that the reed switch Metal detec-tors and article surveillance systems are a problem only if the pacemaker is held directly against the scanner Metal detectors may be triggered at airports by an implanted device Showing the security personnel the identification card is usu-ally sufficient to satisfy them that the patient is not a terrorist; however, a hand search may be conducted to be sure Electric blankets may occasionally cause enough EMI to cause the pacemaker to revert to the interference mode, though this is relatively uncommon

Finally, the issue of cell phones is constantly raised The portable phones that are used in the home present no problem to a pacemaker Cell phones may affect some models of pacemakers There is significant variability between manufactur-ers as to the resistance to EMI from these phones In addition, the newer digital phones that have been used in Europe and are now being introduced into the United States are more likely to cause inhibition of a pacemaker than the analog phones currently in use Studies have shown that if the phone’s antenna is 6 inches

or more away from the pacemaker that it is very unlikely to affect the operation of the pacemaker When patients have a hand held cellular phone we recommend that it be held to the ear opposite the site of the pacemaker implant It is just as important that the phone not be placed in a pocket over the pacemaker while the phone power is on This is because a cellular phone is in constant contact with the local transmitters even if it is not “off the hook”

General instructions regarding the patients disease and symptoms are also re-viewed prior to discharge The indications for the pacemaker implant and basics

of pacemaker function are reviewed Most patients have several common ques-tions that will need to be answered These include:

1 Can I cook with a microwave?

2 What about using household appliances and tools?

3 How long will my pacemaker last?

4 When can I drive?

5 How will I know if my pacemaker malfunctions?

6 What about airport security checks?

7 What happens to my pacemaker when I die?

Most of these questions have been addressed in the preceding section We tell patients that the microwave oven will only harm the pacemaker if the pacemaker

is placed into the oven Since most patients will not fit in a microwave oven the pacemaker is unlikely to be affected Older pacemakers were not encased in metal (which reflects microwaves), and older ovens were not sealed as well as the newer ones It is therefore very uncommon to have a pacemaker affected by this com-mon appliance, even though restaurants and many snack areas in hospitals still

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display a large sign warning pacemaker patients about the presence of the micro-wave oven Most modern pacemakers will last in the range of five to ten years We tell our patients this and explain that it will depend on how the pacemaker is finally programmed and how often they are paced Obviously a pacemaker that is inhibited 90% of the time will last longer than one that paces 90% of the time Some patients and family members have concerns about the pacemaker continu-ing to operate after death has occurred The thought of the person becontinu-ing dead yet the pacemaker continuing to make the heart beat is a chilling thought The fact is that the pacemaker will continue to deliver an impulse to the heart but no con-traction will occur as the muscle ceases to function We get an occasional urgent call from monitored units to turn off the pacemaker because a patient has ex-pired We ask them to turn off their ECG monitor if the pacemaker spikes bother them In rare cases a patient may be near death with the pacemaker simply pro-longing the imminent event The family and physician may then decide that turn-ing off the pacemaker is appropriate

Prior to discharge a temporary pacemaker identification card that is present in the registration material is given to the patient This includes the model, serial number and dates of implant for the pacemaker and lead(s) It also has the name

of the following physician and a contact phone number A copy of the programmed parameters is given as a reference for the patient It is also useful for health care professionals should the patient require medical care elsewhere It is essential that the pacemaker and leads be registered with their manufacturers This assists other physicians in identifying the device and allows the company to track the device should there be a recall or alert Registration is also mandated by Federal law through the Safe Medical Devices Act of 1990

Handbook of Cardiac Pacing, by Charles J Love © 1998 Landes Bioscience

Evaluation of Pacemaker Malfunction

Evaluation of Pacemaker Malfunction 91 Dual Chamber Pacing 99 ACCUFIX/ENCOR Leads 102

EVALUATION OF PACEMAKER MALFUNCTION

The first step in evaluating pacemaker malfunction is to determine if the func-tion of the device is truly abnormal or if one is seeing normal funcfunc-tion of the device By far the largest number of consults we see for malfunctioning pacemak-ers are for devices that are functioning properly With the advent of so many “spe-cial features,” it is easy for even a person experienced with pacemakers to misin-terpret the normal operation of a pacemaker Before one spends a great deal of time attempting to troubleshoot a pacemaker it is imperative that the normal func-tion of the pacemaker be understood This is accomplished by obtaining some basic information about the patient, the device implanted and the programmed parameters (Table 11.1) Many patients carry an identification card that has the information related to the implanted devices Patients occasionally lose their card

or do not bring it with them As a secondary method to identify the device a chest X-ray may be taken Pacemakers have a logo, code or distinct radiographic “skel-eton” that may be matched to a reference text (Fig 11.1) If the manufacturer can

be identified, a call to the manufacturer’s patient registration department can pro-vide the basic information needed Table 11.2 propro-vides phone numbers in the United States for some of the pacemaker companies

As with any medical problem, the history is usually the key to determining the cause of a problem or at least to significantly narrowing the diagnostic options If the problem occurs shortly after implant then lead dislodgment, insufficiently tightened set screws, or poor lead placement should be suspected as a cause rather than battery depletion or lead fracture Conversely, an older device is more likely

to be compromised by lead failure and battery depletion rather than lead dislodgment

The presence or absence of symptoms is very important This will determine if urgent action is required or if the luxury of a more leisurely approach to problem solving is appropriate The first step in a grossly symptomatic patient is to estab-lish a stable cardiac rhythm If the patient is severely bradycardic and the pace-maker programmer is not available or programming changes to the device are ineffective, temporary transvenous pacing should be established as soon as possible

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Table 11.1 Basic troubleshooting data requirements

Pacemaker model

Pacemaker serial number

Lead model(s)

Lead serial numbers(s)

Date of implant for each component

Current programming

Measured data

Lead impedance(s)

Battery voltage and / or impedance

Indication for pacing

Chest X-Ray (if needed or indicated)

Fig 11.1 Radiographic logos can be used to identify a device quickly Either a code that can be deci-phered by using a book or calling a manufacturer, or a model number may be present In this radio-graph the model number 262-14 is clearly seen, instantly identifying the pacemaker.

If necessary, external pacing may be used until a more definitive solution is a-vailable

A tachycardia driven by the pacemaker presents a more difficult situation In most cases application of a magnet or a programming change will terminate the rapid rhythm In rare cases the pacemaker will not respond and urgent surgical intervention may be required for “runaway pacemaker” (Fig 11.2) This uncom-mon malfunction is caused by a major component failure in the pacing circuit The vast majority of rapid pacing rates are caused by a DDD or VDD device tracking

Table 11.2 Phone numbers for pacemaker and ICD manufacturers

Biotronic 800-547-0394

Cardiac Control Systems (CCS) 800-227-7223

Cardiac Pacemakers, Inc (CPI) 800-227-3422

Cordis 800-777-2237

Ela 800-352-6466

In Control 425-861-9301

Medtronic 800-328-2518

Sulzer-Intermedics 888-432-7801

Pacesetter, St Jude 800-777-2237

Telectronics 800-777-2237

Ventritex 800-777-2237

Vitatron 800-848-2876

Fig 11.2 Runaway pacemaker This strip shows VVI pacing at 180 bpm (the runaway protect limit on this device) The pacemaker was programmed to the DDD mode with an upper rate limit of 120 bpm Thera-peutic radiation delivered to the pacemaker in a pateint with breast cancer resulted in circuit failure and rapid pacing Even magnet application did not slow the pacing rate The device was replaced emergently.

atrial fibrillation or flutter The pacemaker will try to track the rapid atrial rate to the upper rate limit of the pacemaker Placing a magnet over the device will drop the pacing rate to the magnet rate of the device until it can be programmed to a nontracking mode such as DDI or VVI Sensor-driven devices may cause rapid pacing as well In one case we found a patient who was experiencing a wide com-plex tachycardia and a tonic-clonic seizure The wide comcom-plex tachycardia was the result of a vibration based sensor-driven pacemaker responding to the seizure Note that it is still quite possible for a patient with an intact AV node to have an atrial arrhythmia with rapid ventricular response Unfortunately the pacemaker

is of little help in this situation Many times the patient and others expect that we will be able to reduce the intrinsic heart rate by reprogramming of the device This is not true and represents a misunderstanding of the function of a pace-maker

After the condition of the patient is stabilized, the history obtained, and the initial data concerning the device is obtained, the ECG is evaluated An approach

to determining the general function of the pacing system is detailed in Table 11.3

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Absence of a pacing output may be caused not only by output problems but also by oversensing An easy way to remember this is that “oversensing causes underpacing, and undersensing causes overpacing.” If the pacemaker is sensing

an electrical event, the pacemaker will be inhibited Often times this is a prema-ture ectopic beat that may be isoelectric on a single monitor lead For this reason multi-lead recordings are needed to evaluate the system properly Oversensing can be diagnosed quickly by placing a magnet over the device If pacing resumes while the magnet is in place then oversensing is a problem If there is no pacing with the magnet on, then either the pacemaker is not putting out a pulse or the pulse is not reaching the heart

Once the nature of the problem is identified, consideration of the possible causes is necessary so that appropriate corrective action may take place It must also be understood that a failing pacemaker may manifest any of the following malfunctions due to the unpredictable nature of circuit failure or the effects of low battery voltage on the circuit Causes of true pacemaker failure are noted in Table 11.4

This potentially life threatening problem is identified by the presence of pace-maker pulse artifact without capture (QRS or P wave) following the impulse (Fig 11.3) Causes of noncapture are listed in Table 11.5

Corrective Action

Increase pacemaker output if possible Where appropriate, revise or replace lead or pacemaker, correct metabolic imbalances For pseudo-noncapture adjust the sensitivity to a more sensitive setting

Table 11.3 Approach to the ECG

1 Pacing

a Spike present

1) Verify appropriate rate interval

2) Verify appropriate depolarization response

a) capture

b) pseudofusion

c) fusion

b Spike absent

1) Apply magnet (magnet function must be enabled)

(Note: a ventricular pacemaker spike falling in the absolute refractory period of the myocardium will NOT result in capture.)

2) Observe on 12 lead ECG for pace artifact and capture

2 Sensing

a Patient must have periods of nonpaced rhythm

b Appropriate escape interval—Hysteresis

3 Compare function to known technical information, observing for end of service indications and other variations

Table 11.4 Causes of pacemaker failure

Battery depletion

Defibrillation near or over the device

Use of electrocautery near or on the device

Random component failure

Severe direct trauma to the device

Therapeutic radiation directed at or near the device

Known modes of failure for devices on recall or alert

Fig 11.3a Atrial noncapture In this dual chamber device, atrial capture is lost as can be seen by the absence of a P wave, and the sudden appearance of a wide complex QRS.

Fig 11.3b Ventricular noncapture Paced output occurs without depolarizing the ventricle resulting in an asystolic pause This pacemaker was programmed to VVI at 70 bpm.

Table 11.5 Common causes of noncapture

Exit block (high-capture threshold)

Inappropriate programming to a low output or pulse width

Lead dislodgment

Lead fracture

Lead insulation failure

Loose connection to pacemaker

Low battery output

Severe metabolic imbalance

Drug effect

“Pseudo-noncapture” (pacing during the refractory period due to undersensing of the preceding complex)

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Recognized by the presence of pulse artifact occurring after an intrinsic event which occurs but does not reset the escape interval (Fig.11.4) This may or may not capture depending on where in the cardiac cycle the pace output falls Causes

of undersensing (thus “overpacing”) are listed in Table 11.6

Corrective Action

Increase pacemaker sensitivity Where appropriate, revise or replace the lead

If the problem is very infrequent then careful observation may be acceptable

Recognized by inappropriate inhibition of the pacemaker in a single chamber system (Fig.11.5) This may be seen as total inhibition of output or as prolonga-tion of the escape interval Myopotentials cause a form of oversensing seen

Table 11.6 Causes of undersensing

Poor lead position with poor R-wave or P-wave amplitude

Lead dislodgment

Lead fracture

Lead insulation failure

Severe metabolic disturbance

Defibrillation near pacemaker

Myocardial infarction of tissue near electrode

Ectopic beats of poor intracardiac amplitude

DVI-committed function

Safety pacing

Fig 11.5 Myopotential inhibition As the patient begins to use the arm on the same side of the pacemaker, the electrical signals of the pectoralis are sensed and mistaken to be QRS signals The device is inhibited until the patient relaxes Note the muscle artifact on the baseline of this rhythm strip.

Fig 11.4 Undersensing This pacemaker is not sensing any of the intrinsic complexes (pacing asynchro-nously) The device is programmed to VVI at 45 bpm with a very low sensitivity setting Note that the 3rd paced output fails to capture as it occurs during the refractory period of the ventricle.

Table 11.7 Causes of oversensing

Myopotentials

Electromagnetic interference

T-wave sensing

Far-field R-wave sensing (atrial lead)

Lead insulation failure

Lead fracture

Loose fixation screw

Crosstalk

Fig 11.6 Myopotential tracking This pacemaker is tracking the patient’s sinus rhythm As the patient begins to use the arm on the same side of the pacemaker, the atrial channel of the pacemaker senses the electrical impulses generated by the pectoralis muscle The pacemaker “tracks” the myopotentials instead

of the P-waves resulting in loss of AV synchrony and rapid ventricular pacing If the myopotentials inhibit the ventricular channel, asystole may result.

predominantly in unipolar pacemakers Inhibition is usually caused by sensing noncardiac muscle activity Myopotentials are typically caused by arm movements

or lifting for prepectoral implants, and by sitting up for abdominal implants In-hibition may also be caused by the ventricular lead sensing the T-wave This “fools” the device into believing a cardiac event has occurred Output is therefore inhib-ited as long as these signals continue Dual chamber systems may exhibit tracking

of electrical signals such as myopotentials This is caused by the same mechanisms

as is inhibition as just discussed (inhibition may occur in either the atrium, ven-tricle or both with a dual chamber pacemaker) However, rapid pacing may be the result of oversensing of electrical signals on the atrial channel that are not strong enough to be sensed on (and thus inhibit) the ventricular channel The atrial chan-nel is usually set to a more sensitive value than the ventricular one What happens

is that an AVI is started each time oversensing occurs triggering a ventricular out-put at a rate up to the programmed URL This is demonstrated by tracking of myopotentials on a unipolar system as shown in Figure 11.6 Additional causes of oversensing are listed in Table 11.7

Corrective Action

Decrease the sensitivity of the device For far-field or T-wave sensing, prolon-gation of the refractory period will correct the problem The sensing polarity may